Engines, including diesel engines, gasoline engines, natural gas engines, and other engines known in the art, may exhaust a complex mixture of air pollutants. The air pollutants may be composed of gaseous and solid material, which include Nitrous Oxides (NOx) and particulate matter. Due to increased attention on the environment, exhaust emission standards have become more stringent. The amount of NOx and particulates emitted from an engine may be regulated depending on the type of engine, size of engine, and/or class of engine.
One method that has been implemented by engine manufacturers to comply with the regulation of particulate matter exhausted to the environment has been to recirculate exhaust gas from an engine back into the engine for subsequent combustion. The recirculated exhaust gas reduces the concentration of oxygen in the intake air supplied to the engine, which in turn lowers the maximum combustion temperature within cylinders of the engine. The reduced temperature decreases the formation of NOx. In addition, the exhaust gases contain some amount of particulate matter, which is burned upon recirculation through the engine cylinders, thereby lowering the amount of particulate matter exhausted to the environment.
When implementing exhaust gas recirculation (EGR), it may be necessary to tightly control the proportion of exhaust gas recirculated through the engine. For example, if the amount of exhaust gas recirculated through the engine is too great, the engine may not receive enough oxygen for proper operation and could possibly stall, produce insufficient levels of power, and/or produce excessive amounts of smoke and particulate matter because of poor combustion within the engine cylinders. Conversely, if the amount of exhaust gas recirculated into the engine is too little, the engine may not comply with exhaust emission regulations.
One method of controlling the ratio of exhaust gas and air supplied to the cylinders of an engine is described in U.S. Pat. No. 5,213,087 (the '087 patent), issued to Sausner et al. on May 25, 1993. The '087 patent describes a device for supplying combusted gases at a controlled rate to the combustion chamber of an internal combustion engine. The device includes a throttle valve and an exhaust gas shut-off valve. The throttle and exhaust gas shut-off valve are operated by a common activating means, which includes a rack and pinion gear configuration and a cam device. The rack is connected to a gas pedal and to the cam device. The throttle valve is connected to the pinion gear to rotate in response to translation of the rack. The exhaust gas shut-off valve is connected to a cam follower to move in response to movement of the cam device. As the gas pedal is moved by an operator, the rack translates to both rotate the pinion gear and move the cam device, thereby adjusting the throttle valve and the exhaust gas shut-off valve.
Although the device of the '087 patent may sufficiently control the rate that combustion gas is supplied to the combustion chamber of the internal combustion engine, it may be complicated, costly, and problematic. In particular, because the device of the '087 patent requires many different components to link the throttle valve and the exhaust gas shut-off valve to the gas pedal, the cost and complexity of the system may increase. In addition, because the exhaust gas shut-off valve is not fixedly connected to the throttle valve, but only connected by way of a cam follower, it may be possible for the cam follower to disconnect from the cam device allowing the exhaust gas shut-off valve to supply an incorrect rate of combustion gas. Further, because the throttle and combustion gas shut-off valves are manually controlled, the engine of the '087 patent may be prone to inefficient operation.
The disclosed throttle and recirculation valve configuration is directed to overcoming one or more of the problems set forth above.